A way of turning text into numbers, so a computer can tell which pieces mean roughly the same thing.
Explanation
The machinery under search that understands what you meant instead of matching the words you typed. Similar is not the same as useful, which is why a second sorting pass usually pays for itself.
Related words
RAG— Looking things up in your own documents and handing the relevant bits to the AI at the moment you ask, instead of hoping it already knew.
reranking— A second sorting step that reorders search results by how well they actually answer the question.